1. Field of the Invention
The invention relates to a method for coding and decoding digitized frames of a special effects film and devices for coding and decoding digitized frames of a special effects film.
2. Prior art
The invention is based on a method for coding digitized frames of a special effects film of the generic type of the independent claim 1.
Previously known coding methods for full-motion pictures are usually defined with relatively few options. The MPEG2 standard has already begun to change this situation since it already allows a relatively large number of optional configurations.
For future standards for coding full-motion pictures, it is desirable that they should allow even more flexibility, making it possible to adapt the coding parameters to the characteristics of the picture material to be coded to an even greater degree than hitherto. In this connection, special parameters for classes of video signals can then also be taken into account which do not occur particularly frequently but can be coded much better by a special choice of parameters.
Such a class of video signals are stroboscope-like alternations of frames from two frame sequences which, for example, occur frequently in the case of music video clips. In such a special effects film, a first number of frames of a first film scene is followed in succession by a second number of a second film scene. As a result of this, frequent scene edits, which in each case provide a completely new picture content, occur in this special effects film. Such a special effects film is digitized and then coded in accordance with the familiar MPEG2 standard, the frequent scene edits cause a high volume of data at the output of the coding device. This is due to the fact that the coding device cannot perform any redundancy compression in the first frame after the scene edit due to a successful motion estimation for various macroblocks of the frame. Thus, a large number of so-called intracoded macroblocks are produced which are coded without temporal prediction in the first frame. Compared with unidirectionally or bidirectionally predictively coded blocks, the data volume of these macroblocks is much larger. In the case of the unidirectionally or bidirectionally predictively coded blocks, only the difference between the macroblock to be transmitted and the motion-compensated macroblock is coded.